What the U.S. will look like if the world heats up beyond 1.5 degrees Climate science shows that beyond 1.5 degrees Celsius of warming, impacts in the U.S. get substantially worse. The world is on track for almost double that level of warming by the end of the century.

3 climate impacts the U.S. will see if warming goes beyond 1.5 degrees

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A MARTÍNEZ, HOST:

There's a number that will be a focus over the next two weeks - 1.5 degrees Celsius. World leaders have agreed that's the limit for how much the planet can warm before the extremes of climate change become insurmountable. But countries are not on track to meet that limit, and they'll discuss this at negotiations in Dubai that begin tomorrow.

So what would the U.S. look like if warming goes beyond that temperature? Lauren Sommer from NPR's climate desk is here to tell us. Lauren, so if the world goes past 1.5 degrees to 2 or 2.5 degrees Celsius, that difference might seem small on paper, and it sounds small when I just said it, but what would it actually look like on the ground?

LAUREN SOMMER, BYLINE: Right, yeah. I mean, half a degree kind of seems minor, but it makes a massive difference in terms of extreme weather in the U.S. and, you know, as a result, the cost to lives and property - because, you know, that number - 1.5 Celsius, which is 2.7 Fahrenheit - it's an average. It takes into account all the temperatures across the planet all year. But warming doesn't happen evenly, and the U.S. is actually heating up faster than that.

MARTÍNEZ: So does that mean if the planet goes beyond 1.5 degrees of warming, the U.S. would get hotter than that?

SOMMER: Yeah, exactly. So say the world reaches 3 degrees Celsius, which is 5.5 Fahrenheit. Parts of the U.S., like Alaska and northern states, would heat up much more - twice as much in some cases. And when it's hotter, that affects the severity of the weather, like extreme storms.

MARTÍNEZ: Yeah. And the U.S. has seen some very destructive hurricanes in recent years. Would that trend keep getting worse?

SOMMER: Yeah, hurricanes, tropical storms are getting more intense. But, you know, so are storms in general because a hotter atmosphere, it can hold more water vapor. I talked to Deanna Hence, an assistant professor at the University of Illinois Urbana-Champaign, and she says that means clouds can drop more rain.

DEANNA HENCE: Every time we have a heavy rainfall event, it's more likely to be even heavier than what we're typically used to seeing.

SOMMER: Hence says, you know, that could mean 30 to 40% more rain in the eastern U.S. from those extreme storms. And that can overwhelm storm drains and infrastructure, and that causes flooding even if you don't live next to a river.

MARTÍNEZ: Wow. I know the U.S. saw some pretty extreme heat waves this year. How much worse do you think those could get if the Earth warms, say, more than 1.5 degrees Celsius?

SOMMER: Yeah, right. I mean, that trend keeps going. So if the world warms 2 degrees Celsius, the southern U.S. could see more than 30 extra days above 95. That's a month more of days like that. And cold days start disappearing, too. The Mountain West could lose 20 to 30 days where it's below freezing.

MARTÍNEZ: Wow. All right, so world leaders meet this week to negotiate how to avoid a future like this. Is it inevitable, really, at this point that the Earth goes beyond 1.5 degrees Celsius?

SOMMER: Yeah, I mean, if countries don't change course. So if we keep burning fossil fuels at the same rate, it looks like the planet will go beyond 1.5 sometime in the next decade. You know, the window of time to avoid that is shrinking. But Deepti Singh, who is an assistant professor at Washington State University, says, you know, it's not too late.

DEEPTI SINGH: We have control over our future. We're not destined to some catastrophic climate. We know that we can have a future that is more equitable and less volatile if we limit the warming through our actions today.

SOMMER: She says every fraction of a degree matters to limit the impacts of climate change. You know, it's not all or nothing. So 1.6 is just as important as 1.5 degrees when it comes to the planet's future.

MARTÍNEZ: That's Lauren Sommer from NPR's climate desk. Lauren, thank you.

SOMMER: Thanks.

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